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Catalytic behavior of metal–organic frameworks in the Knoevenagel condensation reaction

Valentina N. Panchenko, Maria M. Matrosova, Jaewoo Jeon, Jong Won Jun, Maria N. Timofeeva, Sung Hwa Jhung
Journal of catalysis 2014 v.316 pp. 251-259
benzaldehyde, catalytic activity, condensation reactions, coordination compounds, oxygen
Effect of basicity of porous metal-carboxylates, such as MIL-100(Al), Cu3(BTC)2·(H2O)3, UiO-66 and amino-modified UiO-66 materials (UiO-66-NH2) on their catalytic performance, was studied in the Knoevenagel condensation of benzaldehyde with malononitrile to 2-benzylidenemalononitrile. According to physicochemical studies, the strength of the basic sites for MIL-100(Al), Cu3(BTC)2·(H2O)3, UiO-66 was in the range of 830–839kJ/mol, while the amount of basic sites decreased in the order MIL-100(Al)>Cu3(BTC)2·(H2O)3>UiO-66. The insertion of NH2 groups into the UiO-66 framework led to an increase in the strength of basic sites from 839 to 867kJ/mol. The catalytic activity of metal carboxylates correlated with the amount of basic sites and the strength of the interaction between metal and oxygen in the “M⁺ⁿ–O²⁻ Lewis acid–base” pair, which was estimated from ionic covalent parameters. The activity of the UiO-66-NH2 materials was higher than that of UiO-66.